[PATCH kvmtool v2 1/2] cpu: vmexit: Handle KVM_EXIT_UNKNOWN exit reason correctly

["Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org>]

The return value for kernel VM exit handlers is confusing and has led to
errors in different kernel exit handlers. A return value of 0 indicates
a return to the VMM, whereas a return value of 1 indicates resuming
execution in the guest. Some handlers mistakenly return 0 to force a
return to the guest.

This worked in kvmtool because the exit_reason defaulted to
0 (KVM_EXIT_UNKNOWN), and kvmtool did not error out on an unknown exit
reason. However, forcing a VMM exit with error on KVM_EXIT_UNKNOWN
exit_reson would help catch these bugs early.

Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
 kvm-cpu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kvm-cpu.c b/kvm-cpu.c
index f66dcd07220c..7c62bfc56679 100644
--- a/kvm-cpu.c
+++ b/kvm-cpu.c
@@ -170,7 +170,7 @@ int kvm_cpu__start(struct kvm_cpu *cpu)
 
 		switch (cpu->kvm_run->exit_reason) {
 		case KVM_EXIT_UNKNOWN:
-			break;
+			goto panic_kvm;
 		case KVM_EXIT_DEBUG:
 			kvm_cpu__show_registers(cpu);
 			kvm_cpu__show_code(cpu);
-- 
2.43.0